1. Field of the Invention
The present invention relates to an image pickup lens for a solid-state image pickup element that is used in a small-size image pickup device for mobile terminals, PDA (Personal Digital Assistant) devices, and other small-size, thin electronic devices.
2. Description of the Related Art
In recent years, the market for mobile terminals having an image pickup device has grown. Consequently, the image pickup device has begun to incorporate a small-size, high-pixel-number, solid-state image pickup element.
Corresponding to the downsizing and increase in the number of pixels of the imaging element, the image pickup lens is required to have increased performance in view of resolution and image quality, and with wide use thereof, the image pickup lens is also requested to reduce cost.
In order to satisfy a trend for increasing performance, the image pickup lens configured from a plurality of lenses is becoming popular. In comparison with the lens configuration of two to four lenses, the image pickup lens of a five-lens configuration which is capable of increasing performance than in the lens configuration of two to four lenses is also being proposed.
An image pickup lens disclosed, for instance, in JP-A No. 2007-264180 (Patent Document 1) exhibits high performance by including, in the order from an object side, a first lens, a second lens, a third lens, a fourth lens, and a fifth lens. The first lens has a convex surface on the object side and has a positive refractive power. The second lens has a concave surface facing an image side, has a negative refractive power, and has a meniscus shape. The third lens has a convex surface facing the image side, has a positive refractive power, and has a meniscus shape. The fourth lens has an aspherical surface on both sides, has a concave surface on the image side on an optical axis, and has a negative refractive power. The fifth lens has an aspherical surface on both sides and has a positive or negative refractive power.
Further, an image pickup lens disclosed, for instance, in JP-A No. 2007-298572 (Patent Document 2) exhibits high performance by including, in the order from an object side, an aperture stop, a first lens, a second lens, a third lens, a fourth lens, and a fifth lens. The first lens has a positive refractive power. The second lens is joined to the first lens and has a negative refractive power. The third lens has a concave surface facing the object side and has a meniscus shape. The fourth lens has a concave surface facing the object side and has a meniscus shape. The fifth lens has at least one aspherical surface, has a convex surface facing the object side, and has a meniscus shape.
The image pickup lenses described in the Patent Documents 1 and 2 each include five lenses to exhibit high performance. From the viewpoint of their optical length, however, they are not adequately designed to reduce their size and thickness.